1. Field of the Invention
The present invention generally relates to an improvement for power transmission, and particularly relates to an improvement of a transmission for use in an industrial vehicle such as a fork lift or the like having a transmission mechanism of two forward stages and one backward stage, or one forward one stage and two backward stages.
2. Description of the Prior Art
The prior art concerning the present invention is disclosed, for example, in Japanese Patent Unexamined Publication No. 59-110947. As shown in FIG. 2, the prior art transmission is constituted by forward two-stage gear trains, that is, "H" and "L" forward gear trains, and a backward one-stage gear train, that is, an "R" backward gear train. The transmission includes an input shaft 111; an "H" driving gear 112 fixedly mounted on the input shaft 111; an "L" driving gear 113 rotatably mounted on the input shaft 111; and "L" clutch 114 for integrally rotatably connecting the "L" driving gear 113 and the input shaft 111 with each other; an "R" driving gear 115 rotatably mounted on the input shaft 111; an "R" clutch 116 for integrally rotatably connecting the "R" driving gear 115 and the input shaft with each other; an "L" intermediate gear 117 meshed with the "L" driving gear 113; an intermediate shaft 118 on which the "L" intermediate gear 117 is fixedly mounted; an "H" intermediate gear 119 rotatably mounted on the intermediate shaft 118 and meshed with the "H" driving gear 112; and "H" clutch 120 for integrally rotatably connecting the "H" intermediate gear 119 and the intermediate shaft with each other; an intermediate output gear 121 fixedly mounted on the intermediate shaft 118; an output gear 122 meshed with the intermediate output gear 121 and the "R" driving gear 115; and an output shaft 123 provided with the output gear 122. The transmission is arranged to have two, "H" and "L", forward stages and one, "R", backward stage.
In this prior art transmission, certain operational problems have been experienced. That is, it is necessary to separate the shafts 111 and 118 from each other so that the "L" and "H" clutches 114 and 120 do not interfere in each other because the clutch 114 and the clutch 120 are positioned in the direction of the shaft distance in the positional relation to cause an interference therebetween. Therefore, the intershaft distance between the shafts 111 and 118 has been increased, and thereby the whole transmission is increased in size in the direction of the above-mentioned intershaft distance.